Study: (CO), Dehydration and Heat Stress – Full Story

Carbon Monoxide (CO) Exposure and Physiological Stress

In Australia the environment at the race circuit regularly includes factors of high temperature, high solar radiation, and low wind which when combined with Carbon Monoxide (CO) from race car exhaust gases, exerts unique physiological demands on motor sport participants.

For drivers, motor racing demands high levels of concentration for extended periods of time while experiencing high physical loads, radiant heat, exhaust gases and high noise levels. For pit crew and officials it requires high levels of awareness and decision making abilities in an environment of rapidly moving vehicles, noise and exhaust gases.

CO emissions can be high, particularly during periods of incomplete combustion (engine warm ups, engine braking and safety car periods). This may lead to an environment where the combined effects of temperature, dehydration and exhaust fumes could lead to significant decrements in human performance, health and safety.

Carbon Monoxide is an odourless and colourless gas, which the human body possesses no natural means of detecting or responding to effectively which typically leads to symptoms such as drowsiness, fatigue and headaches.

Excessive exposure to CO can cause acute disturbances highly relevant to the task of controlling a racing car, including impaired coordination, reduced accuracy in determining a vehicles position, slower reaction times and impaired ability to attend to multiple tasks. CO also increases sweat rate and temperature rise, thus increasing the effects of hyperthermia and dehydration on psychomotor performance.

To understand the levels of CO exposure and physiological stress at a race event, AIMSS with the collaboration of Monash University commissioned a study to assess carbon monoxide exposure and other environmental and physiological parameters known to influence physiological stress and human performance in a motor sport environment. These parameters were measured in 3 groups of participants (drivers, pit crew, officials) over a 3 day racing event which was part of the Australian V8 Supercar championship (Adelaide 500, Feb 2008).

Thirty subjects (10 drivers, 10 pit crew and 10 officials) participated in the study. Ambient temperature and carbon monoxide concentration was recorded in the pit area and inside vehicles during the event. Driver physiological parameters of blood carboxyhaemoglobin (COHb) concentration, core temperature, hydration status and weight loss were recorded over the race weekend. Blood COHb concentrations were also measured from pit crew and officials.

The recorded data showed that environment carbon monoxide levels were low on average in the pit garage, but reached high levels (>200ppm) for brief periods of 5-10min mainly during engine warm up periods.

Driver cabin CO levels were above 100ppm for significant periods of time (up to 15mins), however V8 drivers are required to use a CO filtering system to supply filtered air to the helmet, so we can presume drivers would be inhaling a lower level of CO than that recorded in cabin.

Blood samples were taken, to measure CO concentration levels in the blood (COHb) for drivers, pit crew and officials after each race. Race 1 levels were 3.4%, 1.4%, and 1.1% respectively with similar values recorded after Race 2, for pit crew and officials and a slightly higher recording of 4.8% for drivers.

Driver core temperatures after Race 1 and Race 2 were 38.7ºC and 39.3ºC respectively and showed evidence of hyperthermic core temperatures (temperatures over 38.5C). However some drivers had near normal levels and with cabin temperatures for the 2 days averaged at 45ºC for Race 1, and 48ºC for Race 2. This variation could be explained by some teams having more effective cooling strategies and the differences in aerobic fitness of the drivers.

Driver hydration status was measured using both Urine Specific Gravity (USG) the morning before each race and weight loss measured after the race. The average driver USG for the morning of Race 1 was 1.020 which is defined as “dehydrated. Drivers were given feedback of these pre Race 1 results and an improvement was noticed for Race 2, however the results still indicated low levels of dehydration on average.

Driver weight changes for Race 1 and 2 showed mean losses of 1.5% and 1.8% of body mass, respectively. There was considerable variation, which indicates some drivers were drinking sufficiently during the race to match sweat loss, other were not.

The results of this study revealed motor sport drivers and pit crew were exposed to significant levels of carbon monoxide for brief periods at this event.

For pit crews peak levels of exposure were during engine warm up periods, so exposure could be dramatically minimised during these periods via improved extraction of exhaust gases and removal of unnecessary personnel from garages.

For drivers a number of strategies could be employed to reduce the exposure levels and physiological stress when driving. In the cabin, improved ventilation and CO filtration systems, advances in cool suits and race suits and of the driver, attention to aerobic fitness and optimum hydration.

Many of these strategies have already been adopted, ongoing development to the various devices continue and new technologies will emerge over time to continue to reduce CO exposure and physiological stress of motor sport participants.